Method of coating cans



July 27, 1937. J. M. l-lo'rl-u-:FesALL- 2,087,974

METHOD 0F COATING CANS A Filed Aug. 2, 1934 7V. ATTORNEYS Patented July27, 1937 UNITED STATES PATENT oF'Fic-E 2,087,974 METHOD oF coA'rIN'GcANs Application August 2, 1934, Serial No. 738,154

2 Claims.

The present invention relates to a method of coating cans and isparticularly directed to the flowing of liquid coating material into andout of the cans being coated so that a coating deposit is left on theirinterior walls.

An object of the present invention is the provision of a method ofcoating cans by introducing a liquid coating material into the interiorof the can which comprises creating a difference of air pressure betweenthe c'an interior and a connected source of supply and then withdrawingthe excess material from the can interior by vreversing the airpressure.

Another object of the invention'is the provision 15 of a method ofcoating cans by employing the can interior as a part of a coatingchamber and .causing the coating material to ow from a source of supplyinto the chamber so formed and over the desired interior can surface byfirst creating a pressure greater than atmospheric on the surface of thecoating material and then reducing this pressure to below atmospheric toremove the excess material from said can.

Another object is the provision of a method of coating cansbymomentarily sealing an open end of a can adjacent a reservoir of liquidcoating material and creating a pressure on the surface of the materialwithin the reservoir. so'that it iiows therefrom and into the caninterior covering the desired surfaces, then syphoning the 73 excessmaterial back into the reservoir leaving the interior can walls coated.

Numerous other objects and advantages of the invention will be apparentas it is better understood from the following description, which, takenin connection with the accompanying drawing, vdiscloses a preferredembodiment thereof.

Referring to the drawing: Figures l-and 2 are sectional views of oneform of apparatus for carrying out the method steps of the instantinvention, Fig. 1 showing a can in position in the apparatus prior tocoating, while Fig. 2 shows the same during coating. l

In coating cans according to the method steps of the instant invention acan having a bottom end is clamped in position between supportingmembers associated with an enclosed tank or reservoir of liquid coatingmaterial. The interior of the positioned can forms part of a coatingchamber which is in direct communication with the coating material inthe tank as by means of passageways and pipes one of the latter beingimmersed in the coating material in the tank.

-A difference of pressure is created between the can interior which isat atmosphere and the interior of the tank which is effected bytheintroduction of compressed air into the tank yabove the coatingmaterial. This air pressure-forces some `of the liquid material from thereservoir and through the pipes and passageways completely filling thepositioned can.

The can is vented as the coating material enters, the vent opening beingassociated with a float valve. The rising liquid passes up and beyondthe can and comes into contact with the valve closing it and blockingoff the vent. 1

The compressedair is now cut olf from thereservoirandvacuumisdrawnonthetank. Theprincipal part of the coatingmaterial in the can and in the coating chamber thereupon Syphens Hthrough the pipes and passageways and returns to the reservoir. As thelevel of the material falls the iloat valve lowers and opens the ventand air again enters bringing the coating chainber to its normalatmospheric pressure.v A portion of the coating material adheres to theinterior surfaces of the 4can including the inner surface of its flangeand a thin, even coating results.

One form of apparatus for performing the steps of the invention isdisclosed in the drawing and comprises a tank Il having a closed bottomI2 and an open top I3. This'constitutes a reservoir for holding a supplyof liquid coating material I4. The top of the tank is closed with acover I which is securely held in place by screws I6.. A fillingaperture in the cover I5 which is closed by a screw lplug I1 is providedfor replenishing the liquid when exhausted.

A flanged can a to be coated is shown as having a bottom end b and thisis obliquely supported adjacent the tank on a rack 2|. The bottom of thecan restson a pad 22 of the rack which is preferably disposed at anangle of approximately 30 degrees .to the horizontal. A ledge 23 extendsup from one side of the pad and engages the side of the can. The rack ismounted on the'top of and is carried by a depending rod 24 which ispreferably connected to any suitable means (not shown) forraising andlowering the rack and can.

With a can in position on the rack 2|, the latter is raised to bring thetop flange of the open end of the can into sealing engagement with ahollow head member 26. Head member 26 is formed with a depending flaredskirt 2l which extends out and over the top of the can and at an anglecorresponding to that of the can top. The skirt near' its bottom edge isprovided with an internal annular channel 28 which provides a seat for aresilient sealing ring 29. It is this ring that the flange of the canseats against and this forms a seal between the can and the hollow headmember. This creates a coating` chamber part of which is formed by thecan interior, while the head interior constitutes the remaining part.

The upper end of the head member is provided with a vent tube 3| whichis adapted to be closed oat times by a. ball oat valve 32. The ballofthe valve is disposed in the skirt of .the head adjacent the lower endof the tube and is suspended from inside the tube.

Forthis purpose the ball hangs from the lower end of a rod 33 whichextends up inside the tube and terminates inv a widened portion havingan elongatedv slot 34. A/pin 35'engages within and extends across theslot and has its ends 'secured in the side walls of the tube. Insuspended position the ball of the valve is below the end of the tube asshown in Fig. 1,;this being the open position of thesvalve.

'I'he head member 26 is preferably supported by the tank cover I landmay be integrally connected with it by a horizontal bracket web 3l. Web31 is formed with a'n axial or horizontal passageway 38 which is closedat both ends, one end being blind, the other closed by a setscrew 39.The passageway forms a connection between a short vertical bore 4|formed in the head and a similar vertical bore 42 formed in the cove l5.Both bores 4|, 42 are formed transverselybff the passageway 38 and areplugged at their upper ends with setscrews 43.

These passageways are utilized in connecting the interior of the coatingchamber with the interior of the tank I for conveying the coatingmaterial into the can. The liquid passes by way of a vertical pipe 45one end of which is threadedly secured in the lower end of the bore 4|.opposite end extends down into the angularly positioned can andterminates in an angularly 'shaped bottom end which reaches into thelowest corner of the can (Fig. 1).

A vertical pipe 41'is located as by a threaded engagement within thelower end of the bore Y 42 and extends down into theY tank and into thecoating liquid. This pipe terminates just short of the tank bottom I2.The coating material is caused to ilow from the tank by way of the pipe41, passageway 38 and pipe 45 and into the coating chamber partiallycomprising the'can a to be coated, by means of an air pressure appliedto the surface ofthe liquid in the reservoir. Control of the-air iseected by a two-way valve 5| threadedly secured at 52 to the top of thecover I5.

One outlet of the valve is by way of a pipe 53 threadedly securedthereto which at its outer end connects with anysuitable source ofcompressed air at a desired pressure. The other outlet of the valve isby way of a threadedly secured pipe 54 the outer yend of which mayconnect with a vacuum pump or the like.

When the valve 5| is turned 4to open communication betweenthe tank andthe pipe 53 (Fig. 2) compressed \air at 4a desired pressure isintroduced into the tank above the coating material. This forces theliquid through the pipe 41, the passageway 38, down the pipe 45 and intothe can, the vent 3| of the coating chamber being open at such a time.

The can is completely 'lled and the coating material rises up and intothe head member 25 and uns che float valve 32 into vent cleans ,Pos1-tion against its seat (Fig. 2). This prevents further flow of the liquidcoating material.

The valve 5| on being turned to its alternate position (Fig. l) cuts offthe compressed air from the reservoir and opens the vacuum supply. Thiseffects a reversal of pressure conditions, the pressure in the tankbeing now reduced to a point lower than atmospheric pressure.Consequently the liquid in the head 26 and can a or most of it ows in areverse direction and is syphoned back into the tank, the recedingliquid opening the vent 3| of the coating chamber by the gravitalmovement of the valve 32.

The return flow of the material drains the can interior of its contentsleaving suiiicient coating material adhering tothe can surfaces toproduce the desired coating. Thus the entire interior surface of thecan, including its flange, is covered with a thin, even coat. 1

It will be understood that gravity may be substituted for vacuum and thevacuum pipe connecticn 54 may be used as a connection to atmosphere.This requires that the relative positions of the coating chamber and thereservoir be changed sothat the level of the liquid in the tank is atall times below the chamber'. In such a variation of apparatus thecompressed air forces the coating material into the can -in the mannerdescribed but when the valve 5| is opened to atmosphere gravity producesthe same syphoningeft'ect and the excess liquid returns to the reservoirleaving the coated can as before.

It is thought that the invention and many of its attendant advantageswill be understood from the foregoing description, and it will beapparent `that various changes maybe made in the steps of the processdescribed and their order of accomplishment without departing from thespirit and scope of the invention or sacricing all of its materialadvantages, the process hereinbefore described being merely a preferredembodiment thereof.

I claim: l

1. A method of liquid coating cans-which consists in supporting a can ininclined position and Y clamping the open outwardly fianged end of thehead space in said closed tank'above the coating material and therebyforcing a portion of said 'liquid into said coating chamber whileventing the latter through said head member, the said coating liquidflowing over the entire interior can surface including the outwardlyanged open end thereof and thence into the head memberthereaboveandlacting to close communication with the atmosphere, thenwithdrawing the excess liquid coating material from said coating chamberand from said can by reducing the fluid pressure in the head space ofsaid tank to below atmospheric pressure, the withdrawal of said excesscoating material from said chamber restoring atmospheric communicationthereof through said head member.

2. A method of liquid coating cans which cona iluid'pressure greaterthan atmosphere to the sists in supporting a can in inclined positionand l of the can and also by said head member, the upper end of saidheadmember being normally open to atmosphere, the interior of the can andheadmember being in communication with a closed tank of liquid coatingmaterial, .introducing a fluid pressure greater than atmosphere to thehead space of said tank above the coating material therein to therebyforce a portion of said liquid into said coating chamber the whileventing the latter, said coating liquid flowing over the entire interiorcan surface including the outwardly anged open endthereof and thenceinto the interior of said head member, closing off said .chamber andfrom atmospheric communication by means of the rising liquid to insurecomplete filling of said f coating chamber to completely coat theinterior of the can and its flange, and then withdrawing a large part ofthe liquid coating from said coating said can and leaving upon theinterior walls of the latter a coating nlm; this withdrawing actionbeing produced by reducing the fluid pressure in the head space of saidtank to below atmospheric pressure, the while again restoring coatingchamber with the atmosphere.

JOHN M. HOTHERSALL.

communication of said

